Feasibility of using near-infrared spectroscopy to diagnose testicular torsion: An experimental study in sheep

Study objective: To assess whether near-infrared spectroscopy can detect testicular hypoxia in a sheep model of testicular torsion within 6 hours of experimental torsion. Methods: This was a randomized, controlled, nonblinded study. Trans-scrotal, near-infrared, spectroscopy-derived testicular tissue saturation of oxygen values were obtained from the posterior hemiscrota of 6 anesthetized sheep at baseline and every 15 minutes for 6 hours after either experimental-side, 720-degree, unilateral, medial testicular torsion and orchidopexy or control-side sham procedure with orchidopexy and then for 75 minutes after reduction of torsion and pexy. Color Doppler ultrasonography was performed every 30 minutes to confirm loss of vascular flow on the experimental side, return of flow after torsion reduction, and preserved flow on the control side. Results: Near infrared spectroscopy detected a prompt, sustained reduction in testicular tissue saturation of oxygen after experimental torsion. Further, it documented a rapid return of these values to pretorsion levels after reduction of torsion. Experimental-side testicular tissue saturation of oxygen fell from a median value of 59% (interquartile range [IQR] 57% to 69%) at baseline to 14% (IQR 11% to 29%) at 2.5 hours of torsion, and postreduction values were approximately 70%. Control-side testicular tissue saturation of oxygen values increased from a median value of 67% (IQR 59% to 68%) at baseline to 77% (IQR 77% to 94%) at 2.5 hours and remained at approximately 80% for the entire protocol. The difference in median testicular tissue saturation of oxygen between experimental and control sides, using the Friedman test, was found to be significant (P=.017). Conclusion: This study demonstrates the feasibility, in a sheep model, of using near-infrared spectroscopy for the noninvasive diagnosis of testicular torsion and for quantification of reperfusion after torsion reduction. The applicability of these findings, from an animal model using complete torsion, to the clinical setting remains to be established.